Power train of automatic transmission

ABSTRACT

A power train of an automatic transmission with eight forward speeds and two reverse speeds includes: a speed reduction unit including a first variable input member connected to an input shaft via a first clutch, first and second variably stopped members connected to a transmission case, and a reduced speed output member; an output unit including a reduced speed input member connected to the reduced speed output member, second and third variable input members connected to the input shaft via second and third clutches, respectively, a third variably stopped member connected to the transmission case, and a shifted speed output member connected to an output gear. A first brake variably stops the third variable stopped member; a second brake variably stops the first variable stopped member; and a third brake variably stops the second variable stopped member.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. patentapplication Ser. No. 11/590,206, filed Oct. 31, 2006, and Korean PatentApplication No. 10-2006-0068026 filed in the Korean IntellectualProperty Office on Jul. 20, 2006, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a power train of an automatictransmission. More particularly, the present invention relates to apower train of an automatic transmission with eight forward speeds andtwo reverse speeds.

(b) Description of the Related Art

A typical shift mechanism of an automatic transmission utilizes acombination of planetary gear sets. A power train of such an automatictransmission changes rotating speed and torque received from a torqueconverter of the automatic transmission, and accordingly changes andtransmits the changed torque to an output shaft.

When a transmission utilizes a relatively large number of shift speeds,speed ratios of the transmission can be optimally designed, andtherefore a vehicle can have better fuel mileage and better performancethan those with fewer shift speeds.

In addition, features of a power train such as durability, efficiency inpower transmission, and size depend a lot on the layout of combinedplanetary gear sets.

A manual transmission with many speeds causes the inconvenience ofexcessively frequent shifting operations by the driver. Therefore,transmissions with large numbers of shift-speeds lend themselves toautomatic transmissions.

In addition, as more speeds are utilized, a power train that can easilyskip up-shift and skip down-shift as well as normally up-shift anddown-shift is required.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present invention provides a power train of an automatictransmission with eight forward speeds and two reverse speeds. The powertrain easily skip up-shifts and skip down-shifts.

A power train of an automatic transmission according to exemplaryembodiments of the present invention includes: an input shaft; an outputgear; a transmission case; a speed reduction unit including a firstvariable input member that is variably connected to the input shaft,first and second variable stopped members that are variably stopped bybeing variably connected to the transmission case, and a reduced speedoutput member that outputs first and second reduced rotational speeds;an output unit including a reduced speed input member that is fixedlyconnected to the reduced speed output member, second and third variableinput members that are variably connected to the input shaft, a thirdvariable stopped member that is variably stopped by being variablyconnected to the transmission case, and a shifted speed output memberthat always acts as an output element by being fixedly connected to theoutput gear. The output unit generates eight forward speeds and tworeverse speeds at the shifted speed output member by operations of thereduced speed input member, the second and third variable input members,and the third variable stopped member; a first clutch for variablyconnecting the first variable input member to the input shaft. The powertrain further includes a second clutch for variably connecting thesecond variable input member to the input shaft; a third clutch forvariably connecting the third variable input member to the input shaft;a first brake for variably stopping the third variable stopped member; asecond brake for variably stopping the first variable stopped member;and a third brake for variably stopping the second variable stoppedmember.

In addition, some embodiments of the present invention further include aone-way clutch disposed between the third variable stopped member andthe transmission case in parallel with the first brake.

According to a first exemplary embodiment of the present invention, thespeed reduction unit includes: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the second sun gear is the firstvariable input member, the first planet carrier is the first variablestopped member, the first sun gear is the second variable stoppedmember, the first ring gear and the second planet carrier are fixedlyconnected to each other and act as the reduced speed output member, andthe first planet carrier is fixedly connected to the second ring gear.

The output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third ring gear is the reduced speedinput member, the fourth sun gear is the second variable input member,the third planet carrier is the third variable input member, the fourthring gear is the third variable stopped member, the fourth planetcarrier is the shifted speed output member, the third planet carrier isfixedly connected to the fourth ring gear, and the third sun gear isfixedly connected to the fourth sun gear.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

According to a second exemplary embodiment of the present invention, thespeed reduction unit includes: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the second ring gear is the firstvariable input member, the first planet carrier is the first variablestopped member, the first sun gear is the second variable stoppedmember, the first ring gear is the reduced speed output member, thefirst ring gear is fixedly connected to the second planet carrier, andthe first sun gear is fixedly connected to the second sun gear.

The output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third sun gear is operated as thereduced speed input member, the fourth sun gear is operated as thesecond variable input member, the third planet carrier and the fourthring gear are fixedly connected to each other and are operated as thethird variable input member, the third planet carrier is operated as thethird variable stopped member, and the third ring gear and the fourthplanet carrier are fixedly connected to each other and act as theshifted speed output member.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

The speed reduction unit of the third exemplary embodiment may be thesame as the speed reduction unit of the first exemplary embodiment.

According to the third exemplary embodiment of the present invention,the output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third sun gear is the reduced speedinput member, the fourth sun gear is the second variable input member,the third planet carrier and the fourth ring gear are fixedly connectedto each other and act as the third variable input member, the thirdplanet carrier is the third variable stopped member, and the third ringgear and the fourth planet carrier are fixedly connected to each otherand act as the shifted speed output member.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

The speed reduction unit of the fourth exemplary embodiment may be thesame as the speed reduction unit of the second exemplary embodiment.

According to the fourth exemplary embodiment of the present invention,the output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third ring gear is the reduced speedinput member, the fourth sun gear is the second variable input member,the third planet carrier is the third variable input member, the fourthring gear is the third variable stopped member, the fourth planetcarrier is the shifted speed output member, the third planet carrier isfixedly connected to the fourth ring gear, and the third sun gear isfixedly connected to the fourth sun gear.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

The speed reduction unit of the fifth exemplary embodiment may be thesame as the speed reduction unit of the second exemplary embodiment.

According to the fifth exemplary embodiment of the present invention,the output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third ring gear is the reduced speedinput member, the fourth sun gear is the second variable input member,the third planet carrier is the third variable input member, the fourthring gear is the third variable stopped member, the fourth planetcarrier is the shifted speed output member, the third planet carrier isfixedly connected to the fourth ring gear, and the third sun gear isfixedly connected to the fourth planet carrier.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

The speed reduction unit of the sixth exemplary embodiment may be thesame as the speed reduction unit of the second exemplary embodiment.

According to the sixth exemplary embodiment of the present invention,the output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the fourth ring gear is the reducedspeed input member, the third sun gear is the second variable inputmember, the third ring gear is the third variable input member, thefourth planet carrier is the third variable stopped member, the fourthsun gear is the shifted speed output member, the third ring gear isfixedly connected to the fourth planet carrier, and the third planetcarrier is fixedly connected to the fourth sun gear.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

According to the seventh exemplary embodiment of the present invention,the speed reduction unit may include: a first planetary gear set havinga first sun gear, a first planet carrier, and a first ring gear; and asecond planetary gear set having a second sun gear, a second planetcarrier, and a second ring gear, wherein the second ring gear is thefirst variable input member, the first planet carrier is the firstvariable stopped member, the first sun gear is the second variablestopped member, the first ring gear is the reduced speed output member,the first ring gear is fixedly connected to the second planet carrier,and the first planet carrier is fixedly connected to the second sungear.

The output unit may include: a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear; and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, wherein the third ring gear is the reduced speedinput member, the fourth sun gear is the second variable input member,the third planet carrier is the third variable input member, the fourthring gear is the third variable stopped member, the fourth planetcarrier is the shifted speed output member, the third planet carrier isfixedly connected to the fourth ring gear, and the third sun gear isfixedly connected to the fourth planet carrier.

The first, second, third, and fourth planetary gear sets may be disposedin a sequence of the first planetary gear set, the second planetary gearset, the third planetary gear set, and the fourth planetary gear set.

According to the eighth exemplary embodiment of the present invention,the speed reduction unit may include a ravingneaux planetary gear sethaving a ravingneaux ring gear, a ravingneaux planet carrier, along-pinion-side sun gear, and a short-pinion-side sun gear, wherein theshort-pinion-side sun gear is the first variable input member, theravingneaux planet carrier is the first variable stopped member, thelong-pinion-side sun gear is the second variable stopped member, and theravingneaux ring gear is the reduced speed output member.

The output unit may include: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the first ring gear is the reduced speedinput member, the second sun gear is the second variable input member,the first planet carrier is the third variable input member, the secondring gear is the third variable stopped member, the second planetcarrier is the shifted speed output member, the first sun gear isfixedly connected to the second sun gear, and the first planet carrieris fixedly connected to the second ring gear.

The ravingneaux planetary gear set and the first and second planetarygear sets may be disposed in a sequence of the ravingneaux planetarygear set, the first planetary gear set, and the second planetary gearset.

According to the ninth exemplary embodiment of the present invention,the speed reduction unit may include a ravingneaux planetary gear sethaving a ravingneaux ring gear, a ravingneaux planet carrier, along-pinion-side sun gear, and a short-pinion-side sun gear, wherein thelong-pinion-side sun gear is the first variable input member, theravingneaux planet carrier is the first variable stopped member, theshort-pinion-side sun gear is the second variable stopped member, andthe ravingneaux ring gear is the reduced speed output member.

The output unit may include: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the first ring gear is the reduced speedinput member, the second sun gear is the second variable input member,the first planet carrier is the third variable input member, the secondring gear is the third variable stopped member, the second planetcarrier is the shifted speed output member, the first planet carrier isfixedly connected to the second ring gear, and the first sun gear isfixedly connected to the second sun gear.

The ravingneaux planetary gear set and the first and second planetarygear sets may be disposed in a sequence of the ravingneaux planetarygear set, the first planetary gear set, and the second planetary gearset.

The speed reduction unit of the tenth exemplary embodiment may be thesame as the speed reduction unit of the eighth exemplary embodiment.

According to the tenth exemplary embodiment of the present invention,the output unit may include: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the first sun gear is the reduced speedinput member, the second sun gear is the second variable input member,the first planet carrier is the third variable input member, the firstplanet carrier and the second ring gear are fixedly connected to eachother and act as the third variable stopped member, the second planetcarrier is the shifted speed output member, and the first ring gear isfixedly connected to the second planet carrier.

The ravingneaux planetary gear set and the first and second planetarygear sets may be disposed in a sequence of the ravingneaux planetarygear set, the first planetary gear set, and the second planetary gearset.

The speed reduction unit of the eleventh exemplary embodiment may be thesame as the speed reduction unit of the ninth exemplary embodiment.

According to the eleventh exemplary embodiment of the present invention,the output unit may include: a first planetary gear set having a firstsun gear, a first planet carrier, and a first ring gear; and a secondplanetary gear set having a second sun gear, a second planet carrier,and a second ring gear, wherein the first sun gear is the reduced speedinput member, the second sun gear is the second variable input member,the first planet carrier is the third variable input member, the firstplanet carrier and the second ring gear are fixedly connected to eachother and act as the third variable stopped member, the second planetcarrier is the shifted speed output member, and the first ring gear isfixedly connected to the second planet carrier.

The ravingneaux planetary gear set and the first and second planetarygear sets may be disposed in a sequence of the ravingneaux planetarygear set, the first planetary gear set, and the second planetary gearset.

The speed reduction unit of the twelfth exemplary embodiment may be thesame as the speed reduction unit of the second exemplary embodiment.

According to the twelfth exemplary embodiment of the present invention,the output unit mau include a ravingneaux planetary gear set having aravingneaux ring gear, a ravingneaux planet carrier, a long-pinion-sidesun gear, and a short-pinion-side sun gear, wherein the long-pinion-sidesun gear is the reduced speed input member, the ravingneaux planetcarrier is the second variable input member, the short-pinion-side sungear is the third variable input member, the ravingneaux planet carrieris the third variable stopped member, and the ravingneaux ring gear isthe shifted speed output member.

The first and second planetary gear sets and the ravingneaux planetarygear set may be disposed in a sequence of the first planetary gear set,the second planetary gear set, and the ravingneaux planetary gear set.

The speed reduction unit of the thirteenth exemplary embodiment may bethe same as the speed reduction unit of the first exemplary embodiment.

According to the thirteenth exemplary embodiment of the presentinvention, the output unit may include a ravingneaux planetary gear sethaving a ravingneaux ring gear, a ravingneaux planet carrier, along-pinion-side sun gear, and a short-pinion-side sun gear, wherein thelong-pinion-side sun gear is the reduced speed input member, theravingneaux planet carrier is the second variable input member, theshort-pinion-side sun gear is the third variable input member, theravingneaux planet carrier is the third variable stopped member, and theravingneaux ring gear is the shifted speed output member.

The first and second planetary gear sets and the ravingneaux planetarygear set may be disposed in a sequence of the first planetary gear set,the second planetary gear set, and the ravingneaux planetary gear set.

The speed reduction unit of the fourteenth exemplary embodiment may bethe same as the speed reduction unit of the second exemplary embodiment.

According to the fourteenth exemplary embodiment of the presentinvention, the output unit may include a compound planetary gear sethaving a long-pinion-side ring gear, a short-pinion-side ring gear, athird planet carrier, and a third sun gear, wherein the long-pinion-sidering gear is the reduced speed input member, the third planet carrier isthe second variable input member, the third sun gear is the thirdvariable input member, the third planet carrier is the third variablestopped member, and the short-pinion-side ring gear is the shifted speedoutput member.

The first and second planetary gear sets and the compound planetary gearset may be disposed in a sequence of the first planetary gear set, thesecond planetary gear set, and the compound planetary gear set.

According to the fifteenth exemplary embodiment of the presentinvention, the speed reduction unit may include a first ravingneauxplanetary gear set having a first ring gear, a first planet carrier, afirst long-pinion-side sun gear, and a first short-pinion-side sun gear,wherein the first short-pinion-side sun gear is the first variable inputmember, the first planet carrier is as the first variable stoppedmember, the first long-pinion-side sun gear is the second variablestopped member, and the first ring gear is the reduced speed outputmember.

The output unit may include a second ravingneaux planetary gear sethaving a second ring gear, a second planet carrier, a secondlong-pinion-side sun gear, and a second short-pinion-side sun gear,wherein the second long-pinion-side sun gear is the reduced speed inputmember, the second planet carrier is the second variable input member,the second short-pinion-side sun gear is the third variable inputmember, the second planet carrier is the third variable stopped member,and the second ring gear is the shifted speed output member.

The first and second ravingneaux planetary gear sets may be disposed ina sequence of the first ravingneaux planetary gear set and the secondravingneaux planetary gear set.

According to the sixteenth exemplary embodiment of the presentinvention, the speed reduction unit may include a first ravingneauxplanetary gear set having a first ring gear, a first planet carrier, afirst long-pinion-side sun gear, and a first short-pinion-side sun gear,wherein the first long-pinion-side sun gear is the first variable inputmember, the first planet carrier is the first variable stopped member,the first short-pinion-side sun gear is the second variable stoppedmember, and the first ring gear is the reduced speed output member.

The output unit may include a second ravingneaux planetary gear sethaving a second ring gear, a second planet carrier, a secondlong-pinion-side sun gear, and a second short-pinion-side sun gear,wherein the second long-pinion-side sun gear is the reduced speed inputmember, the second planet carrier is the second variable input member,the second short-pinion-side sun gear is the third variable inputmember, the second planet carrier is the third variable stopped member,and the second ring gear is the shifted speed output member.

The first and second ravingneaux planetary gear sets may be disposed ina sequence of the first ravingneaux planetary gear set and the secondravingneaux planetary gear set.

According to exemplary embodiments of the present invention, the inputshaft and the output gear may be disposed on the same side.

In addition, the first and third clutches may be disposed between thespeed reduction unit and the output unit, and the second clutch may bedisposed opposite the speed reduction unit with reference to the outputunit.

In addition, the second and third brakes may be disposed opposite thefirst brake with reference to the speed reduction unit.

According to exemplary embodiments of the present invention: the secondclutch, the third brake, and the one-way clutch are operated in a firstforward speed; the second clutch and the second and third brakes areoperated in a second forward speed; the first and second clutches andthe second brake are operated in a third forward speed; the first andsecond clutches and the third brake are operated in a fourth forwardspeed; the first, second, and third clutches are operated in a fifthforward speed; the first and third clutches and the third brake areoperated in a sixth forward speed; the first and third clutches and thesecond brake are operated in a seventh forward speed; the third clutchand the second and third brakes are operated in an eighth forward speed;the first clutch and the first and second brakes are operated in a firstreverse speed; and the first clutch and the first and third brakes areoperated in a second reverse speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a power train of an automatictransmission according to a first exemplary embodiment of the presentinvention;

FIG. 2 is a schematic diagram of a power train of an automatictransmission according to a second exemplary embodiment of the presentinvention;

FIG. 3 is a schematic diagram of a power train of an automatictransmission according to a third exemplary embodiment of the presentinvention;

FIG. 4 is a schematic diagram of a power train of an automatictransmission according to a fourth exemplary embodiment of the presentinvention;

FIG. 5 is a schematic diagram of a power train of an automatictransmission according to a fifth exemplary embodiment of the presentinvention;

FIG. 6 is a schematic diagram of a power train of an automatictransmission according to a sixth exemplary embodiment of the presentinvention;

FIG. 7 is a schematic diagram of a power train of an automatictransmission according to a seventh exemplary embodiment of the presentinvention;

FIG. 8 is a schematic diagram of a power train of an automatictransmission according to an eighth exemplary embodiment of the presentinvention;

FIG. 9 is a schematic diagram of a power train of an automatictransmission according to a ninth exemplary embodiment of the presentinvention;

FIG. 10 is a schematic diagram of a power train of an automatictransmission according to a tenth exemplary embodiment of the presentinvention;

FIG. 11 is a schematic diagram of a power train of an automatictransmission according to an eleventh exemplary embodiment of thepresent invention;

FIG. 12 is a schematic diagram of a power train of an automatictransmission according to a twelfth exemplary embodiment of the presentinvention;

FIG. 13 is a schematic diagram of a power train of an automatictransmission according to a thirteenth exemplary embodiment of thepresent invention;

FIG. 14 is a schematic diagram of a power train of an automatictransmission according to a fourteenth exemplary embodiment of thepresent invention;

FIG. 15 is a schematic diagram of a power train of an automatictransmission according to a fifteenth exemplary embodiment of thepresent invention;

FIG. 16 is a schematic diagram of a power train of an automatictransmission according to a sixteenth exemplary embodiment of thepresent invention;

FIG. 17 is an operational chart for a power train of an automatictransmission with eight forward speeds and two reverse speeds accordingto exemplary embodiments of the present invention;

FIG. 18 is an operational chart for a power train of an automatictransmission with seven forward speeds and two reverse speeds accordingto exemplary embodiments of the present invention; and

FIG. 19 is a lever diagram showing shifting processes from a firstforward speed to an eighth forward speed, and from a first reverse speedto a second reverse speed in the power train of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

As shown in FIG. 1 to FIG. 16, a power train of an automatictransmission according to exemplary embodiments of the present inventionincludes an input shaft 100, which receives torque from an engine (notshown); an output gear 200, which outputs torque from the power train; atransmission case 300; and a speed reduction unit 400, which includes afirst variable input member, first and second variable stopped members,and a reduced speed output member. The speed reduction unit 400generates first and second reduced rotational speeds that are smallerthan a rotational speed of the input shaft 100 at the reduced speedoutput member.

Exemplary embodiments of the power train further include an output unit500, which includes a reduced speed input member, second and thirdvariable input members, a third variable stopped member, and a shiftedspeed output member. The output unit receives torque from the inputshaft 100 and the speed reduction unit 400, and generates eight forwardspeeds and two reverse speeds at the shifted speed output member.

The first variable input member is variably connected to the input shaft100 via a first clutch C1. The second variable input member is variablyconnected to the input shaft 100 via a second clutch C2. The thirdvariable input member is variably connected to the input shaft 100 via athird clutch C3.

The third variable stopped member is variably connected to thetransmission case 300 via a first brake B1 and is subjected to astopping operation of the first brake B1. The first variable stoppedmember is variably connected to the transmission case 300 via a secondbrake B2 and is subjected to a stopping operation of the second brakeB2. The second variable stopped member is variably connected to thetransmission case 300 via a third brake B3 and is subjected to astopping operation of the third brake B3.

The reduced speed output member is fixedly connected to the output unit500. Therefore, the reduced speed output member transmits the first andsecond reduced rotational speeds, which are smaller than the rotationalspeed of the input shaft 100, to the output unit 500.

The reduced speed input member is fixedly connected to the reduced speedoutput member and receives the first and second reduced rotationalspeeds.

The shifted speed output member always acts as an output element bybeing fixedly connected to the output gear 200.

In addition, a one-way clutch F1 disposed between the third variablestopped member and the transmission case 300 is disposed in parallelwith the first brake B1.

In addition, according to the exemplary embodiments of the presentinvention, the input shaft 100 and the output gear 200 are disposed onthe same side, i.e. the speed reduction unit 400, the output unit 500,the clutches C1, C2, and C3, and the brakes B1, B2, and B3 are alldisposed between the transmission case 300 on one side, and the inputshaft 100 and the output gear 200 on the opposite side.

The first and third clutches C1 and C3 are disposed between the speedreduction unit 400 and the output unit 500, and the second clutch C2 isdisposed opposite the speed reduction unit 400 with reference to theoutput unit 500.

The second and third brakes B2 and B3 are disposed opposite the firstbrake B1 with reference to the speed reduction unit 400.

As shown in FIG. 1, according to a first exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. A first pinion gear P1, being engaged with both thefirst ring gear R1 and the first sun gear S1, is connected to andcarried by the first planet carrier PC1.

The second planetary gear set PG2 is a single pinion planetary gear set,and includes a second sun gear S2, a second planet carrier PC2, and asecond ring gear R2. A second pinion gear P2, engaged with both thesecond ring gear R2 and the second sun gear S2, is connected to andcarried by the second planet carrier PC2.

The third planetary gear set PG3 is a single pinion planetary gear set,and includes a third sun gear S3, a third planet carrier PC3, and athird ring gear R3. A third pinion gear P3, engaged with both the thirdring gear R3 and the third sun gear S3, is connected to and carried bythe third planet carrier PC3.

The fourth planetary gear set PG4 is a single pinion planetary gear set,and includes a fourth sun gear S4, a fourth planet carrier PC4, and afourth ring gear R4. A fourth pinion gear P4, engaged with both thefourth ring gear R4 and the fourth sun gear S4, is connected to andcarried by the fourth planet carrier PC4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the first exemplary embodiment of the present invention,the second sun gear S2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and at least one of thefixedly connected first ring gear R1 and the second planet carrier PC2is the reduced speed output member.

The first planet carrier PC1 is fixedly connected to the second ringgear R2, and the second planet carrier PC2 is fixedly connected to thefirst ring gear R1.

In addition, the third ring gear R3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, the thirdplanet carrier PC3 is the third variable input member, the fourth ringgear R4 is the third variable stopped member, and the fourth planetcarrier PC4 is the shifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the third sun gear S3 is fixedly connected to the fourthsun gear S4.

Hereinafter, operations of a power train according to the firstexemplary embodiment of the present invention will be described indetail.

As shown in FIG. 17, according to the first exemplary embodiment of thepresent invention, the second clutch C2, the third brake B3, and theone-way clutch F1 or the first brake B1 are operated in a first forwardspeed D1, the second clutch C2 and the second and third brakes B2 and B3are operated in a second forward speed D2, the first and second clutchesC1 and C2 and the second brake B2 are operated in a third forward speedD3, the first and second clutches C1 and C2 and the third brake B3 areoperated in a fourth forward speed D4, the first, second, and thirdclutches C1, C2, and C3 are operated in a fifth forward speed D5, thefirst and third clutches C1 and C3 and the third brake B3 are operatedin a sixth forward speed D6, the first and third clutches C1 and C3 andthe second brake B2 are operated in a seventh forward speed D7, and thethird clutch C3 and the second and third brakes B2 and B3 are operatedin an eighth forward speed D8.

In addition, the first clutch C1 and the first and second brakes B1 andB2 are operated in a first reverse speed REV. 1, and the first clutch C1and the first and third brakes B1 and B3 are operated in a secondreverse speed REV. 2.

Hereinafter, up-shifting processes of the power train of an automatictransmission according to the first exemplary embodiment of the presentinvention will be described in detail.

In the shifting process from the first forward speed D1 to the secondforward speed D2, the first brake B1 is released and the second brake B2is operated. In the shifting process form the second forward speed D2 tothe third forward speed D3, the third brake B3 is released and the firstclutch C1 is operated. In the shifting process from the third forwardspeed D3 to the fourth forward speed D4, the second brake B2 is releasedand the third brake B3 is operated. In the shifting process from thefourth forward speed D4 to the fifth forward speed D5, the third brakeB3 is released and the third clutch C3 is operated. In the shiftingprocess from the fifth forward speed D5 to the sixth forward speed D6,the second clutch C2 is released and the third brake B3 is operated. Inthe shifting process from the sixth forward speed D6 to the seventhforward speed D7, the third brake B3 is released and the second brake B2is operated. In the shifting process from the seventh forward speed D7to the eighth forward speed D8, the first clutch C1 is released and thethird brake B3 is operated.

Down-shifting processes are reverse processes of the up-shiftingprocesses.

Hereinafter, skip down-shifting processes according to the firstexemplary embodiment of the present invention will be described indetail.

In the skip down-shifting process from the third forward speed D3 to thefirst forward speed D1, the first clutch C1 and the second brake B2 arereleased, and the first brake B1 and the third brake B3 are operated. Inthe skip down-shifting process from the fourth forward speed D4 to thesecond forward speed D2, the first clutch C1 is released and the secondbrake B2 is operated. In the skip down-shifting process from the fourthforward speed D4 to the first forward speed D1, the first clutch C1 isreleased and the first brake B1 is operated. In the skip down-shiftingprocess from the fifth forward speed D5 to the third forward speed D3,the third clutch C3 is released and the second brake B2 is operated.

In the skip down-shifting process from the fifth forward speed D5 to thesecond forward speed D2, 5→4 shifting and 4→2 shifting may be performedin sequence or 5→3 shifting and 3→2 shifting may be performed insequence.

In the skip down-shifting process from the sixth forward speed D6 to thefourth forward speed D4, the third clutch C3 is released and the secondclutch C2 is operated.

In the skip down-shifting process from the sixth forward speed D6 to thethird forward speed D3, 6→5 shifting and 5→3 shifting may be performedin sequence or 6→4 shifting and 4→3 shifting may be performed insequence.

In the skip down-shifting process from the seventh forward speed D7 tothe fifth forward speed D5, the second brake B2 is released and thesecond clutch C2 is operated.

In the skip down-shifting process from the seventh forward speed D7 tothe fourth forward speed D4, 7→6 shifting and 6→4 shifting may beperformed in sequence or 7→5 shifting and 5→4 shifting may be performedin sequence.

In the skip down-shifting process from the eighth forward speed D8 tothe sixth forward speed D6, the second brake B2 is released and thefirst clutch C1 is operated.

In the skip down-shifting process from the eighth forward speed D8 tothe fifth forward speed D5, 8→6 shifting and 6→5 shifting may beperformed in sequence or 8→7 shifting and 7→5 shifting may be performedin sequence.

Skip up-shifting processes are reverse processes of the skipdown-shifting processes.

Alternatively, as shown in FIG. 18, the power train of an automatictransmission according to the first embodiment of the present inventionmay be used for realizing seven forward speeds and two reverse speeds byremoving the eighth forward speed D8.

As shown in FIG. 19, the power train of an automatic transmissionaccording to the first exemplary embodiment of the present inventionincludes four single pinion planetary gear sets. In addition, the firstring gear R1 is fixedly connected to the second planet carrier PC2, andthe second ring gear R2 is fixedly connected to the first planet carrierPC1. The third sun gear S3 is fixedly connected to the fourth sun gearS4, and the third planet carrier PC3 is fixedly connected to the fourthring gear R4. Therefore, operational members of the exemplary powertrain of an automatic transmission according to the first embodiment ofthe present invention are represented as eight nodes in the leverdiagram.

Accordingly, the first sun gear S1 is set to a first node N1, the secondring gear R2 and the first planet carrier PC1 are set to a second nodeN2, the second planet carrier PC2 and the first ring gear R1 are set toa third node N3, the second sun gear S2 is set to a fourth node N4, thethird sun gear S3 and the fourth sun gear S4 are set to a fifth node N5,the fourth planet carrier PC4 is set to a sixth node N6, the thirdplanet carrier PC3 and the fourth ring gear R4 are set to a seventh nodeN7, and the third ring gear R3 is set to an eighth node N8.

As described above, the second sun gear S2 is variably connected to theinput shaft 100 via the first clutch C1. Therefore, rotational speed ofthe engine is delivered to the fourth node N4 through the input shaft100 according to an operation of the first clutch C1.

The first planet carrier PC1 and the first sun gear S1 are variablyconnected to the transmission case 300 via the second and third brakesB2 and B3, respectively. Therefore, the second node N2 and the firstnode N1 may be stopped by operations of the second and third brakes B2and B3, respectively.

Thus, the rotational speed of the engine variably input through thefourth node N4 is changed to the first and second reduced rotationalspeeds at the third node N3 of the first ring gear R1 and the secondplanet carrier PC2 by an operation of the speed reduction unit 400.

In addition, the third ring gear R3 is fixedly connected to at least oneof the fixedly connected first ring gear R1 and the second planetcarrier PC2. Therefore, the eighth node N8 of the third ring gear R3rotates with the same rotational speed of the third node N3.

In addition, the fourth sun gear S4 and the third planet carrier PC3 arevariably connected to the input shaft 100 via the second and thirdclutches C2 and C3. Therefore, the rotational speed of the engine inputthrough the input shaft 100 is delivered to the fifth and seventh nodesN5 and N7 by operations of the second and third clutches C2 and C3,respectively.

In addition, the fourth ring gear R4 is variably connected to thetransmission case 300 via the first brake B1. Therefore, the seventhnode N7 may be stopped by an operation of the first brake B1.

In addition, the fourth planet carrier PC4 is fixedly connected to theoutput gear 200. Therefore, the sixth node N6 outputs each shift speedthat is generated by operations of the speed reduction unit 400 and theoutput unit 500 to the output gear 200.

Hereinafter, formation of each speed by the power train of an automatictransmission according to the first exemplary embodiment of the presentinvention will be described in detail, with reference to FIG. 19.

In the first forward speed D1, the seventh node N7 is stationary sincethe first brake B1 is operated, and the fifth node N5 rotates with thesame rotational speed of the input shaft 100 since the second clutch C2is operated. Therefore, the first forward speed D1 is achieved at thesixth node N6 that is the shifted speed output member.

In the second forward speed D2, the first and second nodes N1 and N2 arestationary since the second and third brakes B2 and B3 are operated.Therefore, the third node N3 is stationary, and the eighth node N8fixedly connected thereto is also stationary. In addition, the fifthnode N5 rotates with the same rotational speed of the input shaft 100since the second clutch C2 is operated. Therefore, the second forwardspeed D2 is achieved at the sixth node N6 that is the shifted speedoutput member.

In the third forward speed D3, the second node N2 is stationary sincethe second brake B2 is operated, and the fourth node N4 rotates with thesame rotational speed of the input shaft 100 since the first clutch C1is operated. Therefore, the third node N3 rotates with the first reducedrotational speed, and the eighth node N8 fixedly connected thereto alsorotates with the first reduced rotational speed. In addition, the fifthnode N5 rotates with the same rotational speed of the input shaft 100since the second clutch C2 is operated. Therefore, the third forwardspeed D3 is achieved at the sixth node N6 that is the shifted speedoutput member.

In the fourth forward speed D4, the first node N1 is stationary sincethe third brake B3, and the fourth node N4 rotates with the samerotational speed of the input shaft 100 since the first clutch C1 isoperated. Therefore, the third node N3 rotates with the second reducedrotational speed, and the eighth node N8 fixedly connected thereto alsorotates with the second reduced rotational speed. In addition, the fifthnode N5 rotates with the same rotational speed of the input shaft 100since the second clutch C2 is operated. Therefore, the fourth forwardspeed D4 is achieved at the sixth node N6 that is the shifted speedoutput member.

In the fifth forward speed D5, the fourth, fifth, and seventh nodes N4,N5, and N7 rotate with the same rotational speed of the input shaft 100since the first, second, and third clutches C1, C2, and C3 are operated.Therefore, the fifth forward speed D5 is achieved at the sixth node N6that is the shifted speed output member.

In the sixth forward speed D6, the first node N1 is stationary since thethird brake B3, and the fourth node N4 rotates with the same rotationalspeed of the input shaft 100 since the first clutch C1 is operated.Therefore, the third node N3 rotates with the second reduced rotationalspeed, and the eighth node N8 fixedly connected thereto also rotateswith the second reduced rotational speed. In addition, the seventh nodeN7 rotates with the same rotational speed of the input shaft 100 sincethe third clutch C3 is operated. Therefore, the sixth forward speed D6is achieved at the sixth node N6 that is the shifted speed outputmember.

In the seventh forward speed D7, the second node N2 is stationary sincethe second brake B2 is operated, and the fourth node N4 rotates with thesame rotational speed of the input shaft 100 since the first clutch C1is operated. Therefore, the third node N3 rotates with the first reducedrotational speed, and the eighth node N8 fixedly connected thereto alsorotates with the first reduced rotational speed. In addition, theseventh node N7 rotates with the same rotational speed of the inputshaft 100 since the third clutch C3 is operated. Therefore, the seventhforward speed D7 is achieved at the sixth node N6 that is the shiftedspeed output member.

In the eighth forward speed D8, the first and second nodes N1 and N2 arestationary since the second and third brakes B2 and B3 are operated.Therefore, the third node N3 is stationary, and the eighth node N8fixedly connected thereto is also stationary. In addition, the seventhnode N7 rotates with the same rotational speed of the input shaft 100since the third clutch C3 is operated. Therefore, the eighth forwardspeed D8 is achieved at the sixth node N6 that is the shifted speedoutput member.

In the first reverse speed REV. 1, the second node N2 is stationarysince the second brake B2 is operated, and the fourth node N4 rotateswith the same rotational speed of the input shaft 100 since the firstclutch C1 is operated. Therefore, the third node N3 rotates with thefirst reduced rotational speed, and the eighth node N8 fixedly connectedthereto also rotates with the first reduced rotational speed. Inaddition, the seventh node N7 is stationary since the first brake B1 isoperated. Therefore, the first reverse speed REV. 1 is achieved at thesixth node N6 that is the shifted speed output member.

In the second reverse speed REV. 2, the first node N1 is stationarysince the third brake B3, and the fourth node N4 rotates with the samerotational speed of the input shaft 100 since the first clutch C1 isoperated. Therefore, the third node N3 rotates with the second reducedrotational speed, and the eighth node N8 fixedly connected thereto alsorotates with the second reduced rotational speed. In addition, theseventh node N7 is stationary since the first brake B1 is operated.Therefore, the second reverse speed REV. 2 is achieved at the sixth nodeN6 that is the shifted speed output member.

The speed line for each planetary gear set will be understood by aperson of an ordinary skill in the art based on the teachings herein.

As shown in FIG. 2, according to a second exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the second exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the third sun gear S3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, at least oneof the fixedly connected third planet carrier PC3 and the fourth ringgear R4 is the third variable input member, the third planet carrier PC3is the third variable stopped member, and at least one of the fixedlyconnected third ring gear R3 and the fourth planet carrier PC4 is theshifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the fourth planet carrier PC4 is fixedly connected to thethird ring gear R3.

As shown in FIG. 3, according to a third exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the third exemplary embodiment of the present invention,the second sun gear S2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and at least one of thefixedly connected first ring gear R1 and the second planet carrier PC2is the reduced speed output member.

The first planet carrier PC1 is fixedly connected to the second ringgear R2, the second planet carrier PC2 is fixedly connected to the firstring gear R1.

In addition, the third sun gear S3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, at least oneof the fixedly connected third planet carrier PC3 and the fourth ringgear R4 is the third variable input member, the third planet carrier PC3is the third variable stopped member, and at least one of the fixedlyconnected third ring gear R3 and the fourth planet carrier PC4 is theshifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the third ring gear R3 is fixedly connected to the fourthplanet carrier PC4.

As shown in FIG. 4, according to a fourth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the fourth exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the third ring gear R3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, the thirdplanet carrier PC3 is the third variable input member, the fourth ringgear R4 is the third variable stopped member, and the fourth planetcarrier PC4 is the shifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the third sun gear S3 is fixedly connected to the fourthsun gear S4.

As shown in FIG. 5, according to a fifth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the fifth exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the third ring gear R3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, the thirdplanet carrier PC3 is the third variable input member, the fourth ringgear R4 is the third variable stopped member, and the fourth planetcarrier PC4 is the shifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the third sun gear S3 is fixedly connected to the fourthplanet carrier PC4.

As shown in FIG. 6, according to a sixth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the sixth exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the fourth ring gear R4 is the reduced speed input member,the third sun gear S3 is the second variable input member, the thirdring gear R3 is the third variable input member, the fourth planetcarrier PC4 is the third variable stopped member, and the fourth sungear S4 is the shifted speed output member.

The third ring gear R3 is fixedly connected to the fourth planet carrierPC4, and the third planet carrier PC3 is fixedly connected to the fourthsun gear S4.

As shown in FIG. 7, according to a seventh exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesthird and fourth planetary gear sets PG3 and PG4.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The third planetary gear set PG3is a single pinion planetary gear set, and includes a third sun gear S3,a third planet carrier PC3, and a third ring gear R3. The fourthplanetary gear set PG4 is a single pinion planetary gear set, andincludes a fourth sun gear S4, a fourth planet carrier PC4, and a fourthring gear R4.

In addition, the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, the third planetarygear set PG3, and the fourth planetary gear set PG4.

According to the seventh exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first planet carrier PC1 is fixedly connected to the secondsun gear S2.

In addition, the third ring gear R3 is the reduced speed input member,the fourth sun gear S4 is the second variable input member, the thirdplanet carrier PC3 is the third variable input member, the fourth ringgear R4 is the third variable stopped member, and the fourth planetcarrier PC4 is the shifted speed output member.

The third planet carrier PC3 is fixedly connected to the fourth ringgear R4, and the third sun gear S3 is fixedly connected to the fourthplanet carrier PC4.

As shown in FIG. 8, according to an eighth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes a ravingneauxplanetary gear set PG, and the output unit 500 includes first and secondplanetary gear sets PG1 and PG2.

The ravingneaux planetary gear set PG includes a ravingneaux ring gearR, a ravingneaux planet carrier PC, a long-pinion-side sun gear LS, anda short-pinion-side sun gear SS. A long pinion gear LP, engaged withboth the long-pinion-side sun gear LS and the ravingneaux ring gear R,and a short pinion gear SP, engaged with both the short-pinion-side sungear SS and the ravingneaux ring gear R, are connected to and carried bythe ravingneaux planet carrier PC.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1.

The second planetary gear set PG2 is a single pinion planetary gear set,and includes a second sun gear S2, a second planet carrier PC2, and asecond ring gear R2.

In addition, the ravingneaux planetary gear set PG and the first andsecond planetary gear sets PG1 and PG2 are disposed in a sequence of theravingneaux planetary gear set PG, the first planetary gear set PG1, andthe second planetary gear set PG2.

According to the eighth exemplary embodiment of the present, theshort-pinion-side sun gear SS is the first variable input member, theravingneaux planet carrier PC is the first variable stopped member, thelong-pinion-side sun gear LS is the second variable stopped member, andthe ravingneaux ring gear R is the reduced speed output member.

In addition, the first ring gear R1 is the reduced speed input member,the second sun gear S2 is the second variable input member, the firstplanet carrier PC1 is the third variable input member, the second ringgear R2 is the third variable stopped member, and the second planetcarrier PC2 is the shifted speed output member.

The first sun gear S1 is fixedly connected to the second sun gear S2,and the first planet carrier PC1 is fixedly connected to the second ringgear R2.

As shown in FIG. 9, according to a ninth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes a ravingneauxplanetary gear set PG, and the output unit 500 includes first and secondplanetary gear sets PG1 and PG2.

The ravingneaux planetary gear set PG includes a ravingneaux ring gearR, a ravingneaux planet carrier PC, a long-pinion-side sun gear LS, anda short-pinion-side sun gear SS. The first planetary gear set PG1 is asingle pinion planetary gear set, and includes a first sun gear S1, afirst planet carrier PC1, and a first ring gear R1. The second planetarygear set PG2 is a single pinion planetary gear set, and includes asecond sun gear S2, a second planet carrier PC2, and a second ring gearR2.

In addition, the ravingneaux planetary gear set PG and the first andsecond planetary gear sets PG1 and PG2 are disposed in a sequence of theravingneaux planetary gear set PG, the first planetary gear set PG1, andthe second planetary gear set PG2.

According to the ninth exemplary embodiment of the present invention,the long-pinion-side sun gear LS is the first variable input member, theravingneaux planet carrier PC is the first variable stopped member, theshort-pinion-side sun gear SS is the second variable stopped member, andthe ravingneaux ring gear R is the reduced speed output member.

In addition, the first ring gear R1 is the reduced speed input member,the second sun gear S2 is the second variable input member, the firstplanet carrier PC3 is the third variable input member, the second ringgear R2 is the third variable stopped member, and the second planetcarrier PC2 is the shifted speed output member.

The first planet carrier PC1 is fixedly connected to the second ringgear R2, and the first sun gear S1 is fixedly connected to the secondsun gear S2.

As shown in FIG. 10, according to a tenth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes a ravingneauxplanetary gear set PG, and the output unit 500 includes first and secondplanetary gear sets PG1 and PG2.

The ravingneaux planetary gear set PG includes a ravingneaux ring gearR, a ravingneaux planet carrier PC, a long-pinion-side sun gear LS, anda short-pinion-side sun gear SS.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2.

In addition, the ravingneaux planetary gear set PG and the first andsecond planetary gear sets PG1 and PG2 are disposed in a sequence of theravingneaux planetary gear set PG, the first planetary gear set PG1, andthe second planetary gear set PG2.

According to the tenth exemplary embodiment of the present invention,the short-pinion-side sun gear SS is the first variable input member,the ravingneaux planet carrier PC is the first variable stopped member,the long-pinion-side sun gear LS is the second variable stopped member,and the ravingneaux ring gear R is the reduced speed output member.

In addition, the first sun gear S1 is the reduced speed input member,the second sun gear S2 is the second variable input member, the firstplanet carrier PC1 is the third variable input member, at least one ofthe fixedly connected first planet carrier PC1 and the second ring gearR2 is the third variable stopped member, and the second planet carrierPC2 is the shifted speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first planet carrier PC1 is fixedly connected to the secondring gear R2.

As shown in FIG. 11, according to an eleventh exemplary embodiment ofthe present invention, the speed reduction unit 400 includes aravingneaux planetary gear set PG, and the output unit 500 includesfirst and second planetary gear sets PG1 and PG2.

The ravingneaux planetary gear set PG includes a ravingneaux ring gearR, a ravingneaux planet carrier PC, a long-pinion-side sun gear LS, anda short-pinion-side sun gear SS. The first planetary gear set PG1 is asingle pinion planetary gear set, and includes a first sun gear S1, afirst planet carrier PC1, and a first ring gear R1. The second planetarygear set PG2 is a single pinion planetary gear set, and includes asecond sun gear S2, a second planet carrier PC2, and a second ring gearR2.

In addition, the ravingneaux planetary gear set PG and the first andsecond planetary gear sets PG1 and PG2 are disposed in a sequence of theravingneaux planetary gear set PG, the first planetary gear set PG1, andthe second planetary gear set PG2.

According to the eleventh exemplary embodiment of the present invention,the long-pinion-side sun gear LS is the first variable input member, theravingneaux planet carrier PC is the first variable stopped member, theshort-pinion-side sun gear SS is the second variable stopped member, andthe ravingneaux ring gear R is the reduced speed output member.

In addition, the first sun gear S1 is the reduced speed input member,the second sun gear S2 is the second variable input member, the firstplanet carrier PCI is the third variable input member, at least one ofthe fixedly connected first planet carrier PC1 and the second ring gearR2 is the third variable stopped member, and the second planet carrierPC2 is the shifted speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first planet carrier PC1 is fixedly connected to the secondring gear R2.

As shown in FIG. 12, according to a twelfth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesa ravingneaux planetary gear set PG.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The ravingneaux planetary gearset PG includes a ravingneaux ring gear R, a ravingneaux planet carrierPC, a long-pinion-side sun gear LS, and a short-pinion-side sun gear SS.

In addition, the first and second planetary gear sets PG1 and PG2 andthe ravingneaux planetary gear set PG are disposed in a sequence of thefirst planetary gear set PG1, the second planetary gear set PG2, and theravingneaux planetary gear set PG.

According to the twelfth exemplary embodiment of the present invention,the second ring gear R2 is the first variable input member, the firstplanet carrier PC1 is the first variable stopped member, the first sungear S1 is the second variable stopped member, and the first ring gearR1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the long-pinion-side sun gear LS is the reduced speed inputmember, the ravingneaux planet carrier PC is the second variable inputmember, the short-pinion-side sun gear SS is the third variable inputmember, the ravingneaux planet carrier PC is the third variable stoppedmember, and the ravingneaux ring gear R is the shifted speed outputmember.

As shown in FIG. 13, according to a thirteenth exemplary embodiment ofthe present invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesa ravingneaux planetary gear set PG.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1 f. The second planetary gear set PG2 is a singlepinion planetary gear set, and includes a second sun gear S2, a secondplanet carrier PC2, and a second ring gear R2. The ravingneaux planetarygear set PG includes a ravingneaux ring gear R, a ravingneaux planetcarrier PC, a long-pinion-side sun gear LS, and a short-pinion-side sungear SS.

In addition, the first and second planetary gear sets PG1 and PG2 andthe ravingneaux planetary gear set PG are disposed in a sequence of thefirst planetary gear set PG1, the second planetary gear set PG2, and theravingneaux planetary gear set PG.

According to the thirteenth exemplary embodiment of the presentinvention, the second sun gear S2 is the first variable input member,the first planet carrier PC1 is the first variable stopped member, thefirst sun gear S1 is the second variable stopped member, and at leastone of the fixedly connected first ring gear R1 and the second planetcarrier PC2 is the reduced speed output member.

The first planet carrier PC1 is fixedly connected to the second ringgear R2, and the second planet carrier PC2 is fixedly connected to thefirst ring gear R1.

In addition, the long-pinion-side sun gear LS is the reduced speed inputmember, the ravingneaux planet carrier PC is the second variable inputmember, the short-pinion-side sun gear SS is the third variable inputmember, the ravingneaux planet carrier PC is the third variable stoppedmember, and the ravingneaux ring gear R is the shifted speed outputmember.

As shown in FIG. 14, according to a fourteenth exemplary embodiment ofthe present invention, the speed reduction unit 400 includes first andsecond planetary gear sets PG1 and PG2, and the output unit 500 includesa compound planetary gear set PG.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1, and afirst ring gear R1. The second planetary gear set PG2 is a single pinionplanetary gear set, and includes a second sun gear S2, a second planetcarrier PC2, and a second ring gear R2. The compound planetary gear setPG includes a long-pinion-side ring gear LR, a short-pinion-side ringgear SR, a third planet carrier PC3, and a third sun gear S3. A longpinion gear LP, engaged with both the long-pinion-side ring gear LR andthe third sun gear S3, and a short pinion gear SP, engaged with both theshort-pinion-side ring gear SR and the third sun gear S3, are connectedto and carried by the third planet carrier PC3.

The first and second planetary gear sets PG1 and PG2 and the compoundplanetary gear set PG are disposed in a sequence of the first planetarygear set PG1, the second planetary gear set PG2, and the compoundplanetary gear set PG.

According to the fourteenth exemplary embodiment of the presentinvention, the second ring gear R2 is the first variable input member,the first planet carrier PC1 is the first variable stopped member, thefirst sun gear S1 is the second variable stopped member, and the firstring gear R1 is the reduced speed output member.

The first ring gear R1 is fixedly connected to the second planet carrierPC2, and the first sun gear S1 is fixedly connected to the second sungear S2.

In addition, the long-pinion-side ring gear LR is the reduced speedinput member, the third planet carrier PC3 is the second variable inputmember, the third sun gear S3 is the third variable input member, thethird planet carrier PC3 is the third variable stopped member, and theshort-pinion-side ring gear SR is the shifted speed output member.

As shown in FIG. 15, according a fifteenth exemplary embodiment of thepresent invention, the speed reduction unit 400 includes a firstravingneaux planetary gear set PG1, and the output unit includes asecond ravingneaux planetary gear set PG2. The first ravingneauxplanetary gear set PG1 includes a first ring gear R1, a first planetcarrier PC1, a first long-pinion-side sun gear LS1, and a firstshort-pinion-side sun gear SS1. The second ravingneaux planetary gearset PG2 includes a second ring gear R2, a second planet carrier PC2, asecond long-pinion-side sun gear LS2, and a second short-pinion-side sungear SS2.

In addition, the first and second ravingneaux planetary gear sets PG1and PG2 are disposed in a sequence of the first ravingneaux planetarygear set PG1, and the second ravingneaux planetary gear set PG2.

According to the fifteenth exemplary embodiment of the presentinvention, the first short-pinion-side sun gear SS1 is the firstvariable input member, the first planet carrier PC1 is the firstvariable stopped member, the first long-pinion-side sun gear LS1 is thesecond variable stopped member, and the first ring gear R1 is thereduced speed output member.

In addition, the second long-pinion-side sun gear LS2 is the reducedspeed input member, the second planet carrier PC2 is the second variableinput member, the second short-pinion-side sun gear SS2 is the thirdvariable input member, the second planet carrier PC2 is the thirdvariable stopped member, and the second ring gear R2 is the shiftedspeed output member.

As shown in FIG. 16, according to a sixteenth exemplary embodiment ofthe present invention, the speed reduction unit 400 includes a firstravingneaux planetary gear set PG1, and the output unit includes asecond ravingneaux planetary gear set PG2.

The first ravingneaux planetary gear set PG1 includes a first ring gearR1, a first planet carrier PC1, a first long-pinion-side sun gear LS1,and a first short-pinion-side sun gear SS1. The second ravingneauxplanetary gear set PG2 includes a second ring gear R2, a second planetcarrier PC2, a second long-pinion-side sun gear LS2, and a secondshort-pinion-side sun gear SS2.

In addition, the first and second ravingneaux planetary gear sets PG1and PG2 are disposed in a sequence of the first ravingneaux planetarygear set PG1, and the second ravingneaux planetary gear set PG2.

According to the sixteenth exemplary embodiment of the presentinvention, the first long-pinion-side sun gear LS1 is the first variableinput member, the first planet carrier PC1 is the first variable stoppedmember, the first short-pinion-side sun gear SS1 is the second variablestopped member, and the first ring gear R1 is the reduced speed outputmember.

In addition, the second long-pinion-side sun gear LS2 is the reducedspeed input member, the second planet carrier PC2 is the second variableinput member, the second short-pinion-side sun gear SS2 is the thirdvariable input member, the second planet carrier PC2 is the thirdvariable stopped member, and the second ring gear R2 is the shiftedspeed output member.

Operations, shifting processes, and formations of each speed of thepower trains according to the second through sixteenth embodiments ofthe present invention are similar to those of the power train accordingto the first embodiment of the present invention, and may be easilyobtained by a person of ordinary skill in the art based on the teachingsherein. Thus, a detailed explanation thereof will be omitted.

According to exemplary embodiments of the present invention, eightforward speeds and two reverse speeds may be realized.

In addition, according to exemplary embodiments of the presentinvention, a skip up-shifting and a skip down-shifting may befacilitated by reducing frictional members engaged or released in a skipshifting process.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1-47. (canceled)
 48. A power train of an automatic transmission,comprising: an input shaft; an output gear; a transmission case; a speedreduction unit comprising a first variable input member that is variablyconnected to the input shaft, first and second variable stopped membersthat are variably stopped by being variably connected to thetransmission case, and a reduced speed output member that outputs firstand second reduced rotational speeds; an output unit comprising areduced speed input member that is fixedly connected to the reducedspeed output member, second and third variable input members that arevariably connected to the input shaft, a third variable stopped memberthat is variably stopped by being variably connected to the transmissioncase, and a shifted speed output member that always acts as an outputelement by being fixedly connected to the output gear, wherein theoutput unit generates eight forward speeds and two reverse speeds at theshifted speed output member by operations of the reduced speed inputmember, the second and third variable input members, and the thirdvariable stopped member; a first clutch for variably connecting thefirst variable input member to the input shaft; a second clutch forvariably connecting the second variable input member to the input shaft:a third clutch for variably connecting the third variable input memberto the input shaft; a first brake for variably stopping the thirdvariable stopped member; a second brake for variably stopping the firstvariable stopped member; a third brake for variably stopping the secondvariable stopped member; and a one-way clutch disposed between the thirdvariable stopped member and the transmission case in parallel with thefirst brake; wherein the speed reduction unit comprises a ravingneauxplanetary gear set comprising a ravingneaux ring gear, a ravingneauxplanet carrier, a long-pinion-side sun gear, and a short-pinion-side sungear; wherein the short-pinion-side sun gear is the first variable inputmember; the ravingneaux planet carrier is the first variable stoppedmember; the long-pinion-side sun gear is the second variable stoppedmember; and the ravingneaux ring gear is the reduced speed outputmember.
 49. The power train of claim 48, wherein the output unitcomprises: a first planetary gear set comprising a first sun gear, afirst planet carrier, and a first ring gear; and a second planetary gearset comprising a second sun gear, a second planet carrier, and a secondring gear; wherein the first ring gear is the reduced speed inputmember; the second sun gear is the second variable input member; thefirst planet carrier is the third variable input member; the second ringgear is the third variable stopped member; the second planet carrier isthe shifted speed output member; the first sun gear is fixedly connectedto the second sun gear; and the first planet carrier is fixedlyconnected to the second ring gear.
 50. The power train of claim 48,wherein the input shaft and the output gear are both disposed at a firstside of the power train.
 51. The power train of claim 48, wherein theravingneaux planetary gear set and the first and second planetary gearsets are disposed in a sequence of the ravingneaux planetary gear set,the first planetary gear set, and the second planetary gear set.
 52. Thepower train of claim 48, wherein the first and third clutches aredisposed between the speed reduction unit and the output unit, and thesecond clutch is disposed opposite the speed reduction unit withreference to the output unit.
 53. The power train of claim 48, whereinthe second and third brakes are disposed opposite the first brake withreference to the speed reduction unit.
 54. The power train of claim 48,wherein: the second clutch, the third brake, and the one-way clutch areoperated in a first forward speed; the second clutch and the second andthird brakes are operated in a second forward speed; the first andsecond clutches and the second brake are operated in a third forwardspeed; the first and second clutches and the third brake are operated ina fourth forward speed; the first, second, and third clutches areoperated in a fifth forward speed; the first and third clutches and thethird brake are operated in a sixth forward speed; the first and thirdclutches and the second brake are operated in a seventh forward speed;the third clutch and the second and third brakes are operated in aneighth forward speed; the first clutch and the first and second brakesare operated in a first reverse speed; and the first clutch and thefirst and third brakes are operated in a second reverse speed. 55-61.(canceled)
 62. The power train of claim 48, wherein the output unitcomprises: a first planetary gear set comprising a first sun gear, afirst planet carrier, and a first ring gear; and a second planetary gearset comprising a second sun gear, a second planet carrier, and a secondring gear; wherein the first sun gear is the reduced speed input member;the second sun gear is the second variable input member; the firstplanet carrier is the third variable input member; the first planetcarrier and the second ring gear are fixedly connected to each other andact as the third variable stopped member; the second planet carrier isthe shifted speed output member; and the first ring gear is fixedlyconnected to the second planet carrier.
 63. The power train of claim 62,wherein the input shaft and the output gear are both disposed at a firstside of the power train.
 64. The power train of claim 62, wherein theravingneaux planetary gear set and the first and second planetary gearsets are disposed in a sequence of the ravingneaux planetary gear set,the first planetary gear set, and the second planetary gear set.
 65. Thepower train of claim 62, wherein the first and third clutches aredisposed between the speed reduction unit and the output unit, and thesecond clutch is disposed opposite the speed reduction unit withreference to the output unit.
 66. The power train of claim 62, whereinthe second and third brakes are disposed opposite the first brake withreference to the speed reduction unit.
 67. The power train of claim 62,wherein: the second clutch, the third brake, and the one-way clutch areoperated in a first forward speed; the second clutch and the second andthird brakes are operated in a second forward speed; the first andsecond clutches and the second brake are operated in a third forwardspeed; the first and second clutches and the third brake are operated ina fourth forward speed; the first, second, and third clutches areoperated in a fifth forward speed; the first and third clutches and thethird brake are operated in a sixth forward speed; the first and thirdclutches and the second brake are operated in a seventh forward speed;the third clutch and the second and third brakes are operated in aneighth forward speed; the first clutch and the first and second brakesare operated in a first reverse speed; and the first clutch and thefirst and third brakes are operated in a second reverse speed. 68-105.(canceled)